Red bosses on green dungeons

So I just soloed Ravensmoor for the first time as a level 54 archer/air mage. As with Kiln, I am once again confused as to why I'm running into a red boss at the end of a green and yellow dungeon. At this point virtually none of the encounters were particularly dangerous. The closest I came to death was trying to handle 2 ghosts and a spider at the same time without getting too close to the other eggs and too far as to invoke the invisible rubber bands. Even the boss's minions weren't much of a threat.

The boss lich himself was red, so my accuracy fell to around 10 - 20% despite wearing dex up gear and casting the dex raising air spell. I won by kiting him in a figure 8 through the two sarcophagi in the front of his arena for around a half hour, despite the camera's attempts to kill me.

As with Kiln, I ask again, what's the point of putting a boss at the end of a dungeon that is either impossible to beat when the dungeon is challenging or possible to beat when the dungeon is trivial?